Eccentric Arm Motion Transmission for Robot Arms

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Solution Overview

Problem

Current motion transmission devices for robot arms, such as reduction gears, face challenges with high costs, complexity, and significant friction due to the need for precise machining of internal toothed gears and crowns, leading to high backlash and wear.

Innovation Solution

A motion transmission device with a shaft and movable member featuring at least three arms with teeth that cooperate with notches, where each arm is articulated on eccentric bearings to ensure constant orientation and engagement with the movable member, reducing friction and backlash through circular trajectories and synchronized rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If internal toothed crowns are used in cycloid reduction gears, then low backlash and reversibility are achieved, but manufacturing complexity and cost increase significantly

Engineering Contradiction:

ImprovebacklashVSAvoidgearbox structure

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent inverts the traditional cycloid gear configuration by placing the toothed crown on the stationary member rather than creating an internal toothing in a ring gear. The arms engage the external teeth of the crown, eliminating the need for complex internal machining while achieving the same reduction ratio and backlash performance.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent replaces expensive, difficult-to-machine internal toothed crowns with simpler external toothed crowns that can be manufactured more economically. The arms with teeth engage these simpler crowns, reducing manufacturing cost while maintaining functional performance.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Manufacturing precision

If internal toothed crowns are used in cycloid reduction gears, then low backlash is achieved, but machining difficulty and cost increase

Engineering Contradiction:

Improvetooth machining precisionVSAvoidcrown machining

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #13The other way round (Inversion)

3Power

If pins and notches are used in crown mechanisms, then movement transmission is achieved, but friction increases significantly

Engineering Contradiction:

Improvemovement transmissionVSAvoidfriction

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

The patent replaces the pin-and-notch mechanical engagement system with a toothed arm engagement system. The teeth on the arms engage the teeth on the crown in a manner similar to conventional gear meshing, reducing friction and improving mechanical efficiency while maintaining the movement transmission function.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Power

If multiple three-arm rotors mounted on eccentrics are used, then movement transmission is achieved, but device complexity and cost increase

Engineering Contradiction:

Improvemovement transmissionVSAvoidmulti-rotor structure

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent merges multiple arm mechanisms into a single rotor structure with multiple arms extending from a common center. This single rotor with multiple arms achieves the same movement transmission function as multiple separate three-arm rotors, significantly simplifying the overall device structure and reducing cost.

Inventive Principle:

Principle #5Merging (Combining)

5Reliability

If elliptical cyclic movement of arm ends is used, then engagement with crown is achieved, but tooth shape definition and machining complexity increase

Engineering Contradiction:

Improveengagement reliabilityVSAvoidtooth machining

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Inventive Principle:

Principle #13The other way round (Inversion)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This design simplifies the machining of teeth and movable member interfaces, reduces friction, and achieves precise motion transmission with low backlash, resulting in a cost-effective and efficient motion transmission system suitable for robot arms with high reduction ratios.

Implementation Method 1

each arm is articulated on a first eccentric bearing relative to a first axis around which the bearing is rotatably mounted... each arm is further articulated on a second eccentric bearing relative to a second axis around which the second bearing is rotatably mounted

Methodology Applied

Scientific EffectEccentric: Eccentric

Data Source

PatentEP3271613A1Movement transmission device, in particular for a robot arm

Publication Date: 2018.01.24 MIP ROBOTICS

AI summary

The device comprises a shaft 4, a notched mobile member - for example a wheel 1 - and at least three arms 2.1, 2.2, 2.3 that together transmit movement between the shaft 4 and the mobile member. Each arm is hinged to two eccentric bearings 3, 3' that hold same parallel to said arm, regardless of the rotational angle of the shaft 4 with which they rotate synchronously. Each arm engages with the notches of the wheel 1 during at least a portion of the cyclic motion of same, by means of at least one tooth 7 of the arm, in such a way as to ensure mutual displacement. The bearings 3, 3' are arranged such that at least one of the arms engages with the mobile member, regardless of the rotational angle of the shaft 4. Said device can be used for producing low-clearance speed reducers.